The Cause of "Cold Snaps."—In a paper read before the American Academy of Science, Prof. Loomis offered a new theory to account for sudden falls of temperature, or "cold snaps," as they are called. The usual mode of accounting for these is by supposing that a current of cold air sets in from the north. A laborious investigation of the subject has led Prof. Loomis to the conclusion that these low temperatures, which occur at irregular intervals in every month, and particularly during the winter, are due mainly to the descent of cold air in the neighborhood, and that this descent of air results from the outward movement, which generally takes place from the centre of an area of high barometer. The theory is fully sustained by observations. As for the opposite theory, if the cold comes to us from the north, "whence does it come," asks Prof. Loomis, "to these colder known points on the earth's surface?" In summer, during a thunder-storm, the temperature often falls 10° in a few minutes, but observations show that there was no air-current from the north. These sudden gusts of cold must descend from the higher atmospheric regions.

School Hygiene.—Dr. Richard Liebreich, the eminent oculist, read a paper on "School Hygiene" at a recent meeting of the London Social Science Association. He spoke of the influence of the posture of children during school-time, restricting himself to the discussion of two points, namely, short-sightedness and lateral curvature of the spine. Short-sightedness, he said, is produced by the lengthening of the anteroposterior axis of the eye, by the increased tension of the apparatus with which we adapt our eyes to different distances. The tension is stronger in proportion as the distance is shorter to which the eye is adjusted. If this power is made use of for adjusting the eye continually to a much shorter distance than would be required; i. e., if, in reading or writing, the eyes, instead of at twelve to fifteen inches, are kept at four to six inches' distance from the book, the sclerotic, or membrane which keeps the globe of the eye in shape, giving way by degrees to the pressure, gradually extends antero-posteriorly. Thus the eye becomes oval, and the retina is somewhat removed from the optic media, from the cornea, and the lens. The retina then only receives the images of near objects; distant objects appear undefined, and can only be seen by the aid of concave glasses.

The abnormal posture of children during school-time, and especially while writing, is productive of spinal curvature. Pupils are forced every day, for several hours, to maintain the same unhealthy posture, overtiring always the same muscles, twisting and bending the spine always at the same place, and thus gradually altering the shape and position of the bones. The normal position would be to keep the upper part of the body straight; the shoulder-blades, both of the same height, freely suspended, together with the upper arm, on the ribs, and in no way supporting the body; both elbows on a level with each other, and almost perpendicular under the shoulder-joint, without any support; only the hands and part of the forearm resting on the table; the weight of the head freely balanced on the vertebral column, and not on any account bent forward, but only turned so much round its horizontal axis that the face may be inclined sufficiently to prevent the angle at which the eye is fixed on the book from being too pointed.

Dr. Liebreich then presents the following design for school desks. The top of the desk has an inclination of 20° for writing; for reading, a greater inclination is required—about 40°. This latter is obtained by turning up a flap of five inches in width, fixed to the front edge of the desk. All seats have backs, consisting only of a board three inches wide, which, placed at the right height, sufficiently supports the lower joints of the spine, to enable the pupil to keep straight while reading or writing. The distance between the back of the seat and the table can be regulated to the size of the pupils, and is always just sufficient for the flap to come quite near the child when writing.

Floating of Solid in Molten Iron.—In a communication to the American Journal of Science, Prof. Adolf Schmidt takes exception to Mr. R. Mallet's explanation of the phenomenon of certain metals in the solid state floating upon a bath of the same metals in a molten state. Mallet assumes the existence of what he terms a "repellent force." Prof. Schmidt upsets this assumption by an experiment which he thus describes: "Have a solid ball of cast-iron of one and a half to two inches diameter cast and filed off pretty smoothly. Have a ladle or vessel of at least three-quarter cubic foot capacity filled with molten cast-iron. If, then, you lay the cold cast-iron ball on the surface of the molten iron, you will find that the ball, in spite of the 'repellent force,' assumed by Mr. Mallet, will sink to the bottom of the ladle at once. With an iron rod you can feel the ball at the bottom of the ladle, and roll it about. But, after twenty or thirty seconds, the ball will slowly rise to the surface of the bath and remain there. It is thus evident that cast-iron, at ordinary temperatures, is both heavier and denser than molten iron, but that, as its temperature rises, the solid iron expands, and becomes lighter, and finally floats on the molten iron. The latter fact shows simply that solid iron, when at a high temperature, approaching its melting-point, is less dense and lighter than molten iron, which fact again implies that molten iron must undergo a rapid expansion in the moment of its solidification. The extent of this expansion is, however, less than that of the subsequent contraction in cooling, so that the cold iron is again denser than the molten iron."

Growth of Plants within the Egg.—Prof. Panceri's observations and experiments on the production, of cryptogamic vegetation in eggs are interesting, from their bearing on the question of spontaneous generation. At Cairo, an ostrich-egg was given him which was still fresh, the airspace having not even been formed. He soon, however, noticed the appearance of dark blotches within the shell, and, having broken it to ascertain the cause, he found that they were produced by the growth of minute fungi. The partisans of spontaneous generation look on such cases as that as an argument in their favor, supposing the shell of an egg to be quite impermeable to germs derived from without. Panceri, on the contrary, has found that the unbroken shell of an egg is permeable to liquids, and that these may introduce germs into the interior. He has, in fact, actually inoculated uncontaminated eggs with a fungus obtained from the interior of one in which it had made its appearance in a way seemingly so mysterious, and which he had cultivated in egg albumen.

Huxley on the Cell-Theory in Physiology.—In seconding a motion of thanks to Prof. Redfern, President of the Biological Section of the British Association, Mr. Huxley said that the promulgation of the cell-theory had as great an effect upon the physiological world as the French Revolution had on the world of politics. Referring to the doctrine promulgated by Schwann and Schleiden, he said that underneath that doctrine there lay the idea which had been established by every further observation, and which remained unassailable, viz., that the living body was not a simple continuous whole, and its action was not the action of a unity, but that it was made up of a multitude of parts, which lived a quasi-independent life; and that the body of a man was made up of an enormous multitude of small living particles, each of which, though subordinated and kept together by means referred to by Prof. Redfern, led a quasi-independent life, as did the cells of the organic elements of a plant. It was, in fact, the application to animal-structure of the idea which had been previously applied to plant-structure.

The Deep-Sea Bottom.—In the "Preliminary Notes" of the Challenger Expedition, presented to the Royal Society of London by Prof. Wyville Thomson, are to be found some observations on the Globigerina and on the sedimentary formations at the bottom of the sea, which mark a substantial advance in the science of these subjects. The globigerina is a minute foraminifer, the shells of which constitute the great bulk of the chalk formation. An ocean sediment known as the "globigerina-ooze" also consists principally of these shells, and hence it is to be regarded as a true chalk formation. Hitherto Prof. Wyville Thomson and Dr. Carpenter have supposed that the globigerina is an inhabitant of the sea-depths, while other English, as well as American and German, naturalists have insisted that it is a surface animal. In these "Preliminary Notes," Prof. Thomson very frankly admits the erroneousness of his own view. In fact, the living globigerina is, he says, very different in appearance from the dead shells we find at the bottom of the sea. In the living animal the shell is clear and transparent, and each of the pores which penetrate it is surrounded by a raised crest, the crest round adjacent pores coalescing with a roughly-hexagonal net-work, so that the pores appear to be at the bottom of an hexagonal pit. At each angle of this hexagon the crest gives off a delicate, flexible, calcareous spine, sometimes four or five times the diameter of the shell in length. These spines radiate symmetrically from the direction of the centre of each chamber of the shell, and the sheaves of long, transparent needles crossing each other in different directions have a very beautiful effect.

The nature of the deposit at the bottom of the ocean appears to depend upon the depth of the superincumbent water. So universally is this the case that the observers on board of the Challenger needed only to know the depth at any locality in order to foretell the character of mud that would there be brought to the surface by the dredging apparatus. According to Prof. Thomson, "the mean maximum depth at which the globigerina-ooze occurs is about 2,250 fathoms. The mean depth at which we find the transition gray ooze is 2,400 fathoms, and the mean depth of the red-clay soundings is about 2,700 fathoms." These three sedimentary formations, however much they differ from each other, are all the result of the precipitation to the bottom of the dead shells of the globigerina and other surface animals. Why, then, do they differ so much in appearance and in chemical constitution? The globigerina-ooze is 98 per cent, carbonate of lime; the gray ooze consists of carbonate of lime with a greater or less proportion of clay; the red ooze is almost pure clay, viz., silica, alumina, and red oxide of iron. Prof. Thomson accounts for the absence of carbonate of lime from the red clay, and its partial absence from the gray ooze, by the theory that at great depths there is an excess of free carbonic acid. This would convert the carbonate of lime of the shells into a soluble compound. In that case the red clay would be "the insoluble residue, the ash, as it were, of the calcareous organisms which form the globigerina-ooze after the calcareous matter has been removed." It is worthy of note that living animals, brought up by the dredge from great depths, have their calcareous shells very rudimentary.

A Ballooning Spider.—A paper of singular interest, by Dr. Lincecum, contributed to the Smithsonian Institution and published in the American Naturalist, describes the marvelous art of the gossamer spider in the construction and navigation of her aëronautical ships. In Texas, according to the author, December is the month for these ballooning spiders to emigrate. When they intend to make an ascension, they fix themselves on some extreme point of the-branch of a tree, or weed, or corn-tassel, then carefully spin out a lock of white gossamer, five or six inches long and two inches wide in the middle, tapering toward the ends, holding it all the time in the gentle breeze by a thread two or three inhces long, which, being attached to the end of the selected point, detains the balloon until it is finished. They then spin out at the bow two lines, thirty or forty feet in length, and another of twenty or thirty feet at the stern, then cut the cable and sail away on an inclined plane. There are a mother and half a dozen or more young spiders aboard every balloon, and thus the species is scattered over vast districts. These tiny aëronauts choose for starting on their voyage a clear day, temperature 60° Fahr., wind gently from the south. At about 1 p. m. they may be seen sailing with the wind. Toward 4 p. m. the spectator will observe that the balloons are beginning to descend. When the streamers strike some tall weed or grass the air-ships are made fast and the passengers instantly leap out, spinning out a thread as they fall, thus landing in safety.

A Demand of Modern Education.—In an address delivered on the occasion of the dedication of Pardee Hall, the scientific school attached to Lafayette College, Prof. Rossiter W. Raymond made some timely remarks upon the absurdity of attempting to complete a young man's education in the same time now as fifty years ago. The enormously-increased demands of modern life, said Prof. Raymond, requiring as they do that a man shall know more things, and know how to do more things, than were formerly sufficient for his reasonable success, are not to be satisfied by a mere change in a few subjects of instruction. It is not enough to substitute one study for another. The period of study must also be prolonged. In recognition of this principle, while it is for the present impracticable to make it an invariable part of a college education, by imperatively increasing the length of the college course, or by raising the standard of admission to colleges, the device of a post-graduate course has been very generally adopted; and it will not be long before experience will demonstrate that those men who have received the most thorough preparatory training are able to overtake and to outstrip in the subsequent race of life those who started with half-developed powers and half-furnished minds.

Insects and Flowers.—In his lecture at Belfast, on "Common Flowers in Relation to Insects," Sir John Lubbock inquired into the causes of flowers closing their petals during rain, and of some flowers remaining open for a longer or shorter period than others. The habit of closing the petals during rain is obviously an advantage, since it prevents the honey being spoilt or washed away. Everybody, however, has observed that even in fine weather certain flowers close at particular hours. This habit of going to sleep is surely very curious: why should flowers do so; and why should some flowers close at the approach of night, and others not? Moreover, flowers keep different hours. The daisy opens at sunrise and closes at sunset, whence its name day's eye; the dandelion opens at seven and closes at live; ear hawkweed is said to wake at eight and go to sleep at two; the scarlet pimpernel wakes at seven and closes soon after two; while Tropogon pratensis opens at four in the morning and closes just before twelve, whence its English name "John-go-to-bed-at-noon." Other flowers, on the contrary, open in the evening. Now, it is obvious that flowers which are fertilized by night-flying insects would derive no advantage from being open by day; nay, it would be a distinct disadvantage, as rendering them liable to be robbed of their honey and pollen by insects not capable of fertilizing them. Hence the lecturer believed that the closing of flowers has reference to the habits of insects. In support of this, he observed that wind-fertilized flowers never sleep, and that some of those flowers which attract insects by smell emit their scent at particular hours.

Catching Cold.—We find, in the Detroit Review of Medicine, an account of Prof. Rosenthal's researches on the effects of sudden changes of temperature, from which we abstract a few very useful observations. It has long been known that "colds" are produced, not by lowness of temperature, but rather by sudden changes from a higher to a lower. The application of cold to the surface of a healthy animal causes the cutaneous vessels to contract, and then the blood is prevented from circulating in the skin, and confined to the interior of the body, where it does not readily lose its heat, but serves to supply warmth to the vital organs. But, if the animal be exposed to heat, the cutaneous vessels become dilated, and so remain after exposure to cold. The blood is thus exposed in large amount over a wide surface, and becomes rapidly cooled, even though the temperature of the surrounding medium is not very low. A sudden passing from a heated room into the cold outer air rapidly cools the blood below the normal degree. As it returns to the internal organs, it cools them much more quickly than it would have done were not the vessels dilated by previous warmth. Thus a sudden cooling of the blood produces an irritating effect, or induces inflammation in a way that a gradual alteration would not do. To produce evil results the cooling must be from above to below the normal temperature. The effect of a chill in causing inflammation may be due partly to the effect of cold on the tissues themselves, and partly to the congestion (hyperæmia) which will occur in some parts when the fluid is driven out of others by the contraction of vessels. Rosenthal lays most stress on the former of these effects. It is a well-known fact that frequent cold bathing or sponging enables one to bear with impunity sudden changes of weather. This is explained by the improved tone of the vessels, produced by the cold applications. Thus, when exposed to heat, they are not so relaxed that they cannot sufficiently contract when necessary.

Blow Plants are distributed.—Some low ground on the banks of the Delaware, below the city of Philadelphia, having had a quantity of mud from the channel of the river spread over it, two species of plants, Polygonum Orientale (an East Indian species), and Cleome pungens (a West Indian species), soon made their appearance in great numbers. During a discussion, in the Philadelphia Academy of Sciences, as to the probable origin of the seeds of these plants, Dr. Leidy expressed the opinion that as the ground had long been used as a place of deposit of ships' ballast, the seeds might have been in the ground previously, and been quickened by the deposit of the mud. Mr. Meehan thought that perhaps the seeds of these plants, protected from air while buried under water, might germinate after exposure to the air. He referred to other cases of the springing up of new plants after the deposit of fresh earth, and suggested a mode of testing the origin of the seeds.

Education and Invention.—There exists a very general belief that great inventions usually come from uneducated men. How erroneous this belief is, at least as regards the art of metallurgy, is well shown by Mr. G. F. Becker, in a lecture delivered in the College of Mines, University of California. Nasmyth, for instance, invented the steam-hammer, without which neither the metallurgist could turn out sound masses of metal of sufficient size for the fabrication of the vast machines now in use for steamships and other purposes, nor the machinist forge them into shape. The crystallization process, and the zinc process for the decolorization of lead, not only enable us to extract at a profit very small proportions of silver and gold, but also produce an admirable quality of lead. Formerly the quality of lead used to depend almost entirely on that of the ore, and the best brands were exported to all parts of the world; now the best of lead may be made from almost any lead-ore. The inventor of the crystallization process, Pattison, was a professional assayer and metallurgist; and Karsten, who invented the zinc process, was a man of great learning and a metallurgist of the first rank. The inventor of the Rachette furnace, "the furnace of the present and probably of the future for lead or copper smelting," is the engineer who controls the whole governmental smelting and mining interests of Russia. Bessemer, the inventor of the process which bears his name, is a man of extensive scientific acquirements; and Siemens, whose most ingenious apparatus for producing very high temperatures has vastly increased our powers of heating iron and steel, of producing all grades of steel, and of distilling zinc, received as perfect an education, scientific and technical, as the world had to offer. It was Faber du Faur, an accomplished Bavarian metallurgist, who first made practical use of the gases which formerly escaped in immense quantities from the tops of blast-furnaces; and the enormous blast-engines, the hoisting-engines, pumps, and hot-blast stoves, often even the roasting-kilns of such establishments, nowadays require no fuel except this long-neglected waste product. Bischof, another engineer, and metallurgical author, was the first to produce gas artificially for smelting purposes; and this was one of the greatest advances ever made in metallurgy. Lundin, a thoroughly educated Swedish metallurgist, has shown how gas may be produced from wet saw-dust, of such power that wrought-iron may be melted with it.

The Temperature of Germination.—Herr F. Haberlandt has published three tables, showing the maximum and minimum germination temperature of all the more important agricultural seeds. He gives the minimum for by far the largest number, including wheat, barley, rye, oats, buckwheat, sugar-beet, linseed, poppy, clover, lucern, peas, rape, and mustard, as below 40.5° Fahr. The minimum for sainfoin, pimpinella, carrot, cumin, sunflower, Sorghum saccharatum, S. vulgare, and maize, is between 40.5° and 51° Fahr.; for tobacco and gourd, between 51° and 60.4° Fahr.; and for cucumber and melon, the minimum lies betweeen 60.4° and 65.3° Fahr. The second table shows the percentage of seeds germinating at the temperatures 61°, 47°, 88°, 100°, 110°, and 122° Fahr., and the number of hours elapsing before the rootlets reached a length of two millimetres (0.07874 inch). The maximum limit for coriander and marjoram is between 77° and 88° Fahr.; for wheat, rye, barley, oats, English ray-grass, vetches, horse-bean, peas, chick-peas, white-mustard, woad, cabbage, late kohl-rabi, turnip, radish, madder, fennel, carrot, cumin, parsley, poppy, linseed, tobacco, and anise seed, between 88° and 100° Fahr.; for the common bean, lupin, clover, lucern, early kohlrabi, summer-rape, buckwheat, chiccory, sunflower, and some varieties of cabbage, between 100° and 110°; and finally, for maize, Sorghum vulgare, panic-grass, turnip-radish, hemp, teasel, gourd, cucumber, and sugar-melon, between 110° and 122° is the maximum. The third table shows the average growth of the rootlets in two days at different temperatures. In all cases there is increased growth from 61° to 77° Fahr.; in many cases, as grasses, clover, mustard, and linseed, a decrease from 77° to 88° Fahr., and in nearly all cases a decrease from 88° to 100° Fahr.

Poisoned Soils.—Trees have been twice planted in a certain square in London, but in both cases died. Dr. Voelcker was accordingly directed by the Royal Horticultural Society to inquire into the cause of this. On examining the clear, watery solution from treating the soil with distilled water, he found that the soil contained one-tenth per cent, of common salt, and two-tenths percent, of nitrates. Whenever the amount of chlorine in soil has reached any thing like an appreciable quantity, it exercises an injurious influence. Land, for example, which has been inundated by the sea, will not grow wheat for the next two years, though in the first year cabbages may be grown, and they will withdraw a good deal of salt from the soil. The quantity of nitrates in the soil under examination was remarkable. Usually, this quantity does not reach a proportion that could be expressed otherwise than by a third place of decimals. There was no doubt, according to Dr. Voelcker, that the two saline ingredients mentioned did the mischief. He did not doubt that the presence of the salt and nitrates was due to the fact that the place was constantly used for committing nuisance. In the same way rabbits kill hedges, and it is well known that it is years before grass will grow in their runs.

Anæsthetics and Metaphysics.—Benjamin Paul Blood has written and printed a little book entitled "The Anæsthetics Revelation and the Gist of Philosophy." His idea seems to be that, when the nervous system is twisted out of its normal function by certain poisons, as it springs back great things are revealed; that is, at the moment a person escapes from anæsthetic stupor he gets a glimpse of the "genius of being"—whatever that may be. Mr. Blood wrote to Tennyson about his discovery, and in his reply the poet says: "I have never had any revelations through anæsthetics; but a kind of 'waking trance' (this for lack of a better word) I have frequently had quite up from boyhood when I have been all alone. This has often come upon me through repeating my own name to myself silently till all at once, as it were, out of the intensity of the consciousness of individuality, the individuality itself seemed to dissolve and fade away into boundless being—and this not a confused state, but the clearest of the clearest, the surest of the surest, utterly beyond words—where death was an almost laughable impossibility—the loss of personality (if so it were) seeming no extinction, but only true life."

The Black Death in Egypt.—According to a correspondent of the Paris Journal des Débats, writing from Egypt, Europe is threatened with a visitation of the black death. The pestilence is said to be spreading rapidly in the neighborhood of Medina and Mecca, its chief feature being the dreaded "plague-spot," which, once it appears, is the sure sign of a fatal termination. The Egyptian Government is exerting itself to the utmost to prevent the spread of the contagion; but, unfortunately, the Ramadan is at hand, when thousands of Mussulman pilgrims flock to the shrine at Mecca, and it is feared that" they will not only help to spread the contagion there, but also bring it back with them to Europe. The greatest anxiety is felt in Italy, on account of its frequent intercourse with Egypt and the coasts of Asia Minor. The only means of averting the danger would be a stringent prohibition to the pilgrims to return direct to the country from which they came; but this measure would require the united action of the European governments, in order to gain the consent of the various Mussulman governments.

The "Voltaic Armadillo."—Regarding the medical use of this contrivance, a leading physician of New York writes us as follows: "I prescribed the voltaic apparatus of Mr. Seibert for one of my patients, a few weeks ago. I have not heard from my patient since, and do not know what effect, if any, resulted. Pulvermacher's chains, I know, have the indorsement of Sir Charles Locock and many other leading physicians of London; but I know nothing personally of their utility. I intend to try the 'Armadillo' again."

We spoke of the "Armadillo" last month, not from any direct knowledge we have of it, but to correct the advertised statement that The Popular Science Monthly had endorsed it, which was not true.

Address to an Atom.

BY AN UNCOMFORTABLY CONSCIOUS AUTOMATON.

Mysterious particle,

Intangible and most indefinite article,
Which even Science cannot fix or focus;
Are you indeed of all this hocus-pocus,
Mischristened Cosmos, protoplast? If so,
'Tis pity that the happy status quo
Of universal dumb inertia ever
Was broken up by vortices or voices,
'Twere surely better far that space had never
Reëchoed to objectionable noises,Or witnessed all this pother
Of biologic bustle, whose chief law seems Bother!Why could not you,
And all your fellow-motes, far, far too prankful,
In the embraces of the boundless blueRest and be thankful?
A plague on all your forces and affinities!A mob of monads, to my notion,
Surpasses one of demons or divinities
Only while idle. With the earliest motion
Began the immitigable Mischief. Why
Must you in chaos cut those primal capers,
Which were "the promise and the potency"
Of—all the woes that fill our morning papers?
'Tis surely a reflection most unpleasant
To think that all the plagues which haunt the present
Spring from that moment in the hidden past,
When the first molecule, weary at last
Of—immemorial motionlessness, stirring,
Jostled his neighbor Atom. What a whirringWent through astounded space!
Thought pictures a grim grin upon the faceOf him, the Prince of Evil;
Only that then, of course, there was no devil.
At least of the New Creed that's one prime article;Though I have little doubt
He was incipient in that self-same particle
Whose fidgets caused the first great stirabout.

If Science's "dry light," at its meridian,
Finds men no more than automatic midges
In its cold ray, the history that bridges
The space between us and the first AscidianWere better blotted.
To archetypal atoms was allotted
An easier fate than to the complex mass
Of clever matter, which has dared to pass
For Man, but is, for all its prayers and panics,
A problem in molecular mechanics!
If Conscience be but chemic combination.
And Love a mere molecular affinity;
What boots all Life's superfluous botheration
Of mad and painful dreams, that limn Divinity
On fool-projected limbos? Life's a swindle,If taken à la Tyndall.
And, let who may in that demoniac war win
("Survival of the fittest!")—yet, as groping
Less anxiously, less fearing, striving, hoping,
An Ape was less a dupe than is a Darwin.
That Atom must be a misguided duffer
Who'd join a Co.; alone it could not suffer.
Why should it long for partnership and pain so?
I would /were a monad—I'd remain so;
And as for "nascent thrills" and "ganglia," drat 'em!
They're things for which I should not care—an Atom!